Add ThemeProvider Implementation for Light and Dark Mode

[tpmst]

This pull request introduces a ThemeProvider using React Context to enable light and dark mode themes across the application. The implementation includes:

• A global ThemeProvider for managing theme state.
• A custom useTheme hook for easy access to the theme and toggle functionality.
• Example usage with a ThemeToggle component for switching themes dynamically.
• Support for extensible custom themes, allowing future enhancement with more themes or styling options.

This addition improves user experience by providing seamless theming and lays the foundation for scalable UI development.